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Release Notes: LLVM FOR RENESAS RL78 10.0.0.202111
Release Notes: LLVM FOR RENESAS RL78 10.0.0.202111
30th of November, 2021
CyberThor Studios Ltd. is releasing the LLVM for Renesas RL78 10.0.0.202111, a cross compiler tool for
Renesas RL78 micro-controllers.
SALIENT FEATURES
The LLVM for Renesas RL78 10.0.0.202111 toolchain is based on:❖ LLVM 10.0.0 [released]❖ Compiler-rt 10.0.0 [released]❖ Libcxx 10.0.0 [released]❖ Libcxx-abi 10.0.0 [released]❖ Newlib 3.1.0 [released]❖ GDB 7.8.2 [released]
LLVM RL78 comes with significant performance improvements (both code size and speed) compared to GCC
RL78. It also comes with support for latest language standards: full support for C17 and C++17 andexperimental support for the C2x (next C standard) and partial support for C++20.
The latest patches are applied to the LLVM sources.

ABOUT LLVM FOR RENESAS RL78 10.0.0.202111
Release Version:

LLVM for Renesas RL78 10.0.0.202111

Release Date:

30th of November, 2021
Ubuntu 18.04 or later (or compatible distribution)

Platforms Supported:
Windows 7 or later
Language:

C, C++

Targets:

G23, G1X, I1X, D1X, LIN MCP, F1X, and L1X

Object File Format:

ELF

CHANGES IN LLVM FOR RENESAS RL78 10.0.0.202111
This toolchain is the successor of GCC RL78 toolchain, and it is meant as a direct replacement to GCC RL78.
This section describes the fixes made in the LLVM for Renesas RL78 10.0.0.202111 release.
1. [Improvement] llvm-objdump does not display symbol name instead of raw address where possible.
llvm-objdump was not displaying symbol names instead of raw address where possible. This made thedisassembly slightly harder to read than in case of rl78-elf-objdump. The issue is now fixed.
2.

[Improvement] ASM printer and emitter error reporting

The ASM printer now prints an error when wrong assembly code is used instead of a stack dump.
3.

[Improvement] Added __sectop/__secend address operators

Using the -frenesas-extensions option, __sectop("section-name") / __secend("section-name") will return thestart and end + 1 addresses of the specified section.
4.

[Bug Fix] std::bitset class not working correctly

The std::bitset class was not working correctly. This issue has now been fixed.
Notes:
This installer does not provide an option to integrate the LLVM RL78 toolchain with e2 studio, as the e2studio IDE will automatically detect the LLVM RL78 toolchain installation on start-up for integration.
Alternatively, you may use the 'Toolchain Management' feature in e2 studio to achieve this.
For details on e2 studio please visit the following link below:
https://www.renesas.com/eu/en/software-tool/e-studio
There is no support in this installer to integrate toolchain with the HEW IDE.

KNOWN ISSUES IN LLVM FOR RENESAS RL78 10.0.0.202111
The following is a list of known issues for the tools we include for the LLVM for Renesas RL78 10.0.0.202111
toolchain:
1. Assembly parsing issue of callt instruction operand.
The assembly parser cannot handle any complex expressions as operands for callt instruction, only constantvalues are allowed at the moment.
2. Assembly parsing of %lo16, %hi16 limited support.
When using %lo16, %hi16 operators only 2 basic operations are currently allowed, symbol + constant andsymbol - constant.
For example:.short %lo16(_my_symbol) + %lo16(my_const)
The parse will be enhanced in future versions to support more complex expressions.
3. Assembly parsing missing operand.
There is currently no assembly operand to extract 8-bit data from symbols in order to be used with MOV ES,#byte, MOV CS, #byte etc. Only immediate values can be used with those instructions at the moment. The
current workaround is to use %lo16, %hi16 to set the value in 16-bit register and then move the relevant
part in ES/CS. A new operand will be implemented in next release.
4. -finput-charset=/-fexec-charset= unsupported character encodings.
Unlike GCC, Clang accepts only UTF-8 encoding (which is also the default) as valid arguments for -finputcharset and -fexec-charset options. More encoding will be added in future releases.
5. Missing assembly listing support (-a[cdhlns] option in GNU AS).
There’s no equivalent in the LLVM for the -a[cdhlns] GNU AS option.
The alternative solution is to use llvm-objdump to obtain source code interleaved with assembly (-S, --source
option).
6. Unsigned bitfields not supported.
Currently, there is no support for unsigned bitfields in LLVM. This will be implemented in a future release.
7. Binding of references to packed fields.
Creating references to struct members which are declared as packed, e.q. __attribute__ ((packed)), isincorrect as it can cause unaligned access issues. The compiler should return an error in this case however
this is not currently the case. This will be fixed in a future release.
8. Warnings generated using -mfar-rom option.

When using -mfar-rom the linker will generate several warnings like "warning: incompatible rodata area
flags...". The root cause of this issue is that there are no prebuilt libraries with this option. The same issue
exists in GCC with the corresponding option, -mes0, the differences being that GCC ignores the problem
silently. There are currently no known issues caused by this however this will be investigated further in next
release and handled accordingly.
9. llvm-objdump missing features
llvm-objdump does not currently support -i and -g options supported by rl78-elf-objdump. This will be fixed
in a future release.
10. Inline assembly missing constraints and modifiers support for parameters.
Clang supports, in case of RL78, inline assembly constructs without parameters, e.q. asm(AssembleTemplate).
The extended syntax available in GCC, asm (AssemblerTemplate : OutputOperands : InputOperands :Clobbers : GotoLabels), is not currently supported. This will be fixed in the next release, however theconstraints will not be the same as in GCC.

11. Other issues, non-specific to RL78
LLVM tries to be a complete replacement. As such there are still a couple of missing features from GCC
which will be implemented in future releases. In particular, the following issues should be noted:
lld: Information printed using --print-gc-sections is not as nice as when using the GNU ld. Bug 46783
llvm-ar: Errors when printing multiple members with the same name. Bug 42521
llvm-dwarfdump: Does not print section attribute flags yet. Bug 38488
llvm-nm: Unable to understand symbols built with gcc-lto Bug 41437
llvm-nm: Needs support for --line-numbers to llvm-nm Bug 40001
llvm-objcopy: Unknown argument '--change-section-address'. Bug 45217
llvm-objcopy: Objcopy zero-size section might cause huge binaries. Bug 46299
llvm-objdump: Prints wrong line number info for obj file compiled with -ffunction-sections. Bug 40703
llvm-objdump: Wrong behavior for non-relocatable objects when suing llvm-objdump with -r option. BugBug 41901
llvm-readobj: Make GNU style symbol printing invalid symbol section indexes match GNU readelf Bug 43850
llvm-readelf: Relocation addends printed style does not match GNU readelf Bug 45235
llvm-string: Short option with argument grouping not GNU compatible Bug 42942

llvm-string: Allow "-<integer>" as an alias for "-n <integer>" Bug 42964
llvm-symbolizer: Shows incorrect source line info if --gc-sections used Bug 41124
llvm-symbolizer: llvm-addr2line does not exit when passed a non-existent file Bug 42754
12. Other issues
Finally, for better understanding regarding the status of the toolchain please visit https://bugs.llvm.org/ .
In particular, the following queries will help better understand the status of each tool.
https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=ELF&product=lld&query_format=advanced&resolution=--https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=llvm-ar&product=tools&query_format=advanced&resolution=--https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=llvmdwarfdump&product=tools&query_format=advanced&resolution=--https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=llvm-nm&product=tools&query_format=advanced&resolution=--https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=llvmobjcopy%2Fstrip&product=tools&query_format=advanced&resolution=--https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=llvm-objdump&product=tools&query_format=advanced&resolution=-https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=llvm-readobj&product=tools&query_format=advanced&resolution=--https://bugs.llvm.org/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=CONFIRMED&
bug_status=REOPENED&component=llvm-size&product=tools&query_format=advanced&resolution=--https://bugs.llvm.org/buglist.cgi?bug_status=NEW&bug_status=CONFIRMED&bug_status=REOPENED&com
ponent=llvm-symbolizer&product=tools&query_format=advanced&resolution=---FREE SUPPORT FOR LLVM FOR RENESAS RL78 10.0.0.202111
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